linux-kernel - Re: [PATCH 1/3] xen/pv: allow pmu msr accesses to cause GP

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Date:   Tue, 27 Sep 2022 07:42:36 +0200
From:   Juergen Gross <jgross@...e.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xenproject.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 1/3] xen/pv: allow pmu msr accesses to cause GP

On 26.09.22 22:09, Boris Ostrovsky wrote:
> 
> On 9/26/22 10:18 AM, Juergen Gross wrote:
>>   bool pmu_msr_read(unsigned int msr, uint64_t *val, int *err)
>>   {
>>       if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
>> -        if (is_amd_pmu_msr(msr)) {
>> -            if (!xen_amd_pmu_emulate(msr, val, 1))
>> -                *val = native_read_msr_safe(msr, err);
>> -            return true;
>> +        if (!is_amd_pmu_msr(msr))
> 
> 
> You should be able to move vendor check inside is_<vendor>_pmu_msr().

I like that. Together with Jan's suggestion this makes the code much
more readable!


Juergen


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